1. Field of the Invention
The present invention generally relates to a method for fabricating a semiconductor device. More particularly, the present invention generally relates to a method for forming an interconnection line in a semiconductor device and an interconnection line structure.
A claim is made to Korean Patent Application No. 2004-5520, filed Jan. 28, 2004, the contents of which are hereby incorporated by reference.
2. Description of the Related Art
As the design rule for semiconductor devices has gotten smaller, the density of interconnection lines to interconnect and drive components has increased, and the width of interconnection lines has decreased. As a result, parasitic capacitance has increased due to the reduction in space between interconnection lines. In addition, interconnection line resistance has increased due to the reduction in the cross sectional area of the interconnection line. Increase in the interconnection line resistance and the parasitic capacitance cause Resistance-Capacitance delay (RC delay), which slow electrical signals throughout a circuit. The RC delay slows the total operational speed of the semiconductor device and increases power consumption. The RC delay must be overcome in order to implement highly integrated semiconductor devices.
Interconnection line resistance is reduced by employing a conductive material having low specific resistance; copper is a suitable interconnection line material in a damascene process. The damascene process is classified into a single damascene process and a dual damascene process. A conventional single damascene process is disclosed in U.S. Pat. No. 4,944,836, and a conventional dual damascene process is disclosed in U.S. Pat. No. 4,789,648. U.S. Pat. No. 6,057,239 discloses a conventional dual damascene process using a sacrificial filling layer.
To reduce the parasitic capacitance, an interlayer insulating layer or an inter-metallic insulating layer formed from a low-k dielectric material such as an organo silicate glass (OSG) is employed to isolate the interconnection lines. However, low-k dielectric materials have poor mechanical and chemical properties as compared to silicon oxide. As a result, when an interconnection line is formed with a low-k dielectric material interlayer insulating layer or an inter-metallic insulating layer is used, the low-k dielectric layer deteriorates during a subsequent plasma type dry etching or planarization process. Thus, in order to prevent the low-k dielectric layer from deteriorating, an oxide capping layer is formed on the low-k dielectric layer.
However, carbon within the low-k dielectric layer reacts with oxygen during the plasma process. Oxygen is used as an oxidizing agent when forming the oxide capping layer. Oxidation of the low-k dielectric layer creates porous properties on the surface of the layer. As a result, a serious under cutting of the low-k dielectric layer occurs during a wet cleaning process. The wet cleaning process is used after a trench or via hole is formed within the low-k dielectric layer by patterning an oxide capping layer and the low-k dielectric layer. Moreover, if the dielectric constant of the low-k dielectric layer is changed, the reliability of the semiconductor device is degraded.